1. Field of the Invention
This invention relates to a wand type bar code reader for reading bar code information by scanning an object with a visible laser beam emitted from a semiconductor laser.
2. Description of the Prior Art
Heretofore, so-called wand type (pen type) bar code readers have been known. An optical system of a conventional wand type bar code reader 1 is constructed as schematically shown in FIG. 8. In FIG. 8, the reference character 1a denotes a pen casing of the wand type bar code reader 1. A light emitting diode (LED) 2 and the photo detector 3 are disposed within the pen casing 1a. The pen casing 1 is provided at its tip with an optical condenser 4. The wand type bar code reader 1 contacts the object when scanning. A bar code pattern is printed on the object. An illuminating light to be emitted from the LED 2 illuminates a bar code pattern through the optical condenser 4 and the illuminating light is reflected by the bar code pattern. The reflected light is guided again into the pen casing 1a through the optical condenses (focus lens) 4. The wand type bar code reader 1 has an optical fiber 5 here and the reflected light is guided to the photo detector 3 through the optical fiber 5. The information on the bar code pattern is read based on the change in the reflected quantity of light guided to the photo detector 3.
However, a shortcoming of this conventional wand type bar code reader is that the readable range is extremely narrow. Therefore, if the surface of the object has large irregularities, the reading of the information on the bar code pattern becomes impossible because the change in distance between the surface of the object and the converging lens 4 is large.